Scanning beam deflection system and method

Abstract

A scanning beam deflection system and method utilizes a beam scanning device for producing rays diverging from a central axis of a beam of charged particles and a deflection magnet assembly for deflecting the scanning beam substantially 270° within an evacuated deflection chamber such that the deflected scanning beam exits an offset beam window in the deflection chamber and has rays diverging from the central axis of the deflected scanning beam at substantially the same angle as the diverging rays produced by the beam scanning device. The system and method is particularly useful for irradiating internal surfaces of hollow articles with the deflection chamber and deflection magnet assembly disposed along an axis of symmetry of the object.

What is claimed is: 
     
       1. A system for uniformly irradiating an object with a beam of charged particles comprising means for forming a narrow beam of electrons directed along a predetermined central axis,   an evacuated chamber positioned to receive said beam and having an exit window generally parallel to said central axis,   first deflection means disposed between said means for forming and said evacuated chamber for deflecting said beam through predetermined angles to both sides of said central axis, and   second deflection means located at said evacuated chamber for rotating said beam through approximately 270° to exit through said window at the same angle relative to the undeflected beam as said beam bore to said central axis upon entering said evacuated chamber.   
     
     
       2. A system for uniformly irradiating an object as recited in claim 1 wherein second said deflection means includes magnetic pole means having a leading edge arranged at an angle of substantially 45° to the central axis of said scanning beam upon entering the magnetic field of said magnetic pole means. 
     
     
       3. A system for uniformly irradiating an object as recited in claim 2 wherein said magnetic pole means includes spaced parallel pole pieces coupled with a flux return yoke. 
     
     
       4. A system for uniformly irradiating an object as recited in claim 3 wherein said pole pieces have electrical windings wound thereon. 
     
     
       5. A system for uniformly irradiating an object as recited in claim 1 and further comprising focusing magnet means disposed along the path of the beam before said first deflection means for controlling the width of said scanning beam at said second deflection means. 
     
     
       6. A system for uniformly irradiating an object as recited in claim 1 further comprising an object having an annular surface to be irradiated;   means disposing said annular surface generally symmetrically with respect to said central axis with a region on said annular surface in the path of said scanning beam exiting said beam window; and   means for rotating said annular surface about said central axis.   
     
     
       7. A method of uniformly irradiating an internal surface of a hollow object having an axis of symmetry comprising the steps of scanning a beam of charged particles;   directing a central axis of the scanning beam of charged particles parallel to the axis of symmetry of the object;   deflecting all elements of the scanned beam substantially 270° by deflection means positioned within the object to produce a deflected scanning beam substantially transverse to the undeflected scanning beam; and   rotating the object and the deflection means relative to one another about the central axis of the beam to circumferentially irradiate the internal surface of the object with the deflected scanning beam.   
     
     
       8. The method as recited in claim 7 wherein said step of deflecting the scanning beam includes deflecting the scanning beam with magnet means producing a field arranged at an angle of substantially 45° to the central axis of the scanning beam. 
     
     
       9. A low profile apparatus for irradiating in a plane parallel to the axis of a source of charged particles comprising accelerator means for producing a beam of charged particles,   said accelerator means disposed along and producing a beam directed along a first axis,   means adapted to support material to be irradiated in a plane parallel to said axis;   beam scanning means for scanning the beam about said axis,   a beam exit window disposed parallel to said axis,   evacuated deflection chamber means receiving the scanning beam along said axis, and   deflection means disposed at said deflection chamber means for deflecting said scanning beam regardless of the angle of entry into said deflection chamber means through substantially 270° to cause said scanning beam to exit through said exit window directed at said support means at the same angle relative to an undeflected beam as said beam bore to an undeflected beam upon entry into said deflection chamber.   
     
     
       10. A low profile apparatus as recited in claim 9 and further comprising a second beam exit window disposed transverse to and intercepting said axis and second means adapted to support material to be irradiated in a plane transverse to said axis, said deflection means being selectively energized to cause said scanning beam to exit through said first mentioned exit window directed at said first mentioned support means and de-energized to permit said scanning beam to pass directly through said evacuated deflection chamber means and said second exit window directed at said second support means.